Heat propagation in thermally conductive polymers of PA6 and hexagonal boron nitride

Thermally conductive polymers offer new possibilities for the heat dissipation in electric and electronic components, for example, by a three‐dimensional shaping of the heat sinks. To face safety regulations, improved fire performance of those components is required. In contrast to unfilled polymers, those materials exhibit an entirely different thermal behavior. To investigate the flammability, a phosphorus flame retardant was incorporated into thermally conductive composites of polyamide 6 and hexagonal boron nitride. The flame retardant decreased the thermal conductivity only slightly. However, the burning behavior changed significantly, due to a different heat propagation, which was investigated using a thermographic camera. An optimum content of hexagonal boron nitride for a sufficient thermal conductivity and fire performance was found between 20 and 30 vol%. The improvement of the fire performance was due to a faster heat release out of the pyrolysis zone and an earlier decomposition of the flame retardant. For higher contents of hexagonal boron nitride, the heat was spread faster within the part, promoting an earlier ignition and increasing the decomposition rate of the flame retardant.     

Light-induced electron spin polarization in the ground state of water-soluble copper porphyrins

Light-induced spin-polarized transient EPR spectra are reported for several water-soluble copper porphyrins. The spectra are assigned to the doublet ground state, with emissive spin polarization resulting from photoexcitation and subsequent electronic relaxation. In contrast to other systems for which polarization of a doublet ground state has been observed, the exchange interactions in the copper porphyrins are strong and the geometry is fixed. It is proposed that intersystem crossing from the photoexcited trip-doublet to the trip-quartet state can lead to net polarization of the spin system and that this polarization is maintained during electronic decay, possibly via charge-transfer and exciplex states. The intensity of the observed spin polarization is essentially independent of the molecular orientation in the external field, but is strongly dependent on the nature of the charged peripheral groups. Possible reasons for this behavior are discussed.     

Zur Fließfähigkeit von Schüttgütern – Definition und Meßverfahren

Flowability of Bulk Solids – Definition and Measuring Principles . The flowability of bulk solids has to be known for many practical applications. The present paper describes how the flowability is defined and on which physical properties it depends. Experimental determination of the flowability using a shear test is demonstrated. Conditions influencing measuremed results are described. Finally an overview of various methods used for characterization of the flowability of bulk solids is given.     

Vital-Fluorochromization of Microorganisms Using 3′,6′-Diacetylfluorescein to Determine Damages of Cell Membranes and Loss of Metabolic Activity by Ozonation

Cell suspensions of Escherichia coli as a model for bacterial populations in wastewaters were treated with ozone as a disinfectant in a continuously operated pilot plant with a plug flow reactor. Suspensions with an initial number of CFU (colony forming units) of 10⁸ mL^?1 were ozonized with ozone concentrations up to 12 mg/L. Metabolic activities and membrane functions break down with increasing ozone concentrations. The fluorochromization using 3′,6′-diacetylfluorescein (FDA) proved to be a suitable method for the detection of an alteration in permeability of the cell membranes and an inactivation of metabolic activity. By fluorescence microscopic and photometric investigations it could be clearly demonstrated that, in the case of disinfection with ozone, inactivation of the cells includes first of all a damage of the cell membranes. In contrast to the determination of the number of CFU, fluorochromization allows the detection of alteration in metabolic activities.     

Lung cancer--hopelessness in inoperability? A 10-year follow-up

BACKGROUND: According to reports of Durrant et al. [19] and Berry et al. [5] it was concluded that non-operable non-small cell lung tumors cannot be cured. In this consequence initiation of radiotherapy was fixed at the beginning of symptoms. However, long-time survivors in our follow-up lead us to analyse not only quality of life and secondary therapeutic effects but also this special group with the results of the whole collective treated in the same period of interest. PATIENTS AND METHODS: Between 1.1. 1981 and 31. 12. 1983 a number of 169 patients had been recommended for locoregional radiotherapy treatment of lung cancer; 145 patients received at least 50 Gy, 134 out of them 60 Gy or more. Men/female ratio was 137:8, median age was 65 (36 to 88) years. Classified according to the TN-stage there were 59 patients in T1-4 N0 and 86 patients in T1-4 N1-3 M0. Histologically: 98 squamous cell carcinomas, 23 adenocarcinomas, 9 large cell carcinomas and 15 specimens mixed from the named subgroup or rare histologies. Treatment concept including repetition of bronchoscopic evaluation after 60 Gy was prospectively discussed and fixed with our pneumologist. Radiation dose was given with a shrinking-field technique to mediastinum and primary. In case of macroscopically or microscopically persistence of tumor we continued radiation dose up to 80 Gy. Radiotherapy was not followed by chemotherapy. A telecobalt unit has been used for treatment due to the lack of high-voltage linear accelerators. In absence of a computer assisted planning system-a problem in most of the radiotherapeutic centers in this time-dose calculation was done by central beam planning of ICRU-point in the middle of the tumor respectively the center of target volume on the base of a cross section. Usually there was used a 3-field plan ap/pa opposite and an oblique field with an angle of 30 degrees from the ipsilateral back or ventral side, depending on the position of the tumor. Spinal cord was shielded to avoid a dose-more than 36 to 42 Gy. The longer distance and higher weightiness of the oblique fields had as consequence lung fibrosis in the irradiated lung area and a considerable higher maximal dose situated in the soft tissue and skin often followed by strong indurations in this area 1 to 3 years after radiation therapy without further limitations of quality of life. RESULTS: From 145 patients with non-small cell lung cancer 64.1% (93/145) survived 6 months, 42.8% (62/145) 1 year, 19.3% (28/145) 2 years and 7.6% (11/145) 5 and 4.8 (7/145) more than 10 years. According to TN-stages T1-4 N0 collective had a survival rate of 67.8% (40/59) after half a year, 50.8% (30/59) after 1 year, 23.7% (14/59) after 2 and 11.9% (7/59) after 5 years. Treatment results by patients with positive lymph nodes T1-4 N1-3 after the same intervals are: 61.6% (53/86), 37.2% (32/86), 16.2% (14/86) respectively 4.7% (4/86). In the period 5 to 10 years after irradiation 4 patients died, 1 with local relapse, 2 with contralateral lung cancer-ipsilateral region was endoscopically and histologically free of tumor- and 1 patient in consequence of heart insufficiency of several years. Seven patients are still alive after 13 to 16 years. There is no sign of tumor in this group or any effects limitating their quality of life. Twenty-four patients received less than 50 Gy. All patients but 2 did not survive 6 months. One patient survived half a year and 1 patient 2 years. CONCLUSIONS: The reported treatment results in a period with modest technological possibilities, a telecobalt unit, should encourage to a curative intention, when dissemination cannot be proved. If lung cancer is limited to the primary region with or without lymph node metastases the possibility of tumor elimination is small but feasible. If inoperable lung cancer is not curable, this mostly is not due to inability of locoregional radiotherapy, but rather can be seen as a lack of reliable and permanent elimination or prevention of     

Machining of reproducible flaws corresponding to fatigue cracks for fracture mechanics tests of components and welded joints

In connection with the analysis and the development of failure concepts in fracture mechanics for quasistatic loaded components and elastic-plastic behaviour of the material, tests are also carried out with welded and/or complex shaped specimens or structures. Thereby the difficulty arises of generating reproducible flaws in the form of fatigue precracks in definite positions in the components, respectively in the welded joint. It is reported exemplarily about experiments on different CT25 and CCT specimens and on a pressure vessel which contained a fatigue pre-crack, a 0.2 mm saw cut or notches with notch root radius ≤ ≥ 0.1 mm as flaws. The comparison of the results with regard to J-integral at initiation of stable crack, J_i, and J_R curves shows that under certain conditions the 0.2 mm saw cut (notch root radius ≤ ≤ 0.02 mm) is a useful alternative, if reproducible generation of a fatigue pre-crack will not be successful or too expensive. The tests were carried out on StE 460 and on a welded joint of this steel at 25 ± 2°C.     

Higher order modes on usual waveguides

In the following paper some different kinds of microwave guides will be inspected under main aspect of higher order modes. The knowledge of these modes is important for field matching problems at discontinuities and for suppressing propagation of higher order modes by geometrical variations. In some cases it is sufficient to know their principal behaviour. They will be calculated in paper by the often used orthogonal expansion. This method allows to determine all kinds of waves: propagating, damping and complex waves. The following guides are inspected:

1. rectangular waveguides,
2. circular waveguides,
3. L-shaped waveguides,
4. double ridged rectangular waveguides,
5. unilateral finlines with one slot,
6. unilateral finlines with two slots,
7. shielded microstrip lines,
8. circular image guides,
9. rectangular waveguides with dielectric slab,
10. H-guides.